At least two functional specific cell types have been implicated in the initiation of antibody synthesis. One of these appears to be responsible for the recognition of antigens while the other synthesizes the antibody. Recent studies suggest that immunologically tolerant animals possess a normal complement of antibody forming cells but may lack recognition cells. It is the purpose of this project to: l) demonstrate the presence or absence of specific recognition cells in tolerant versus normal animals; 2) demonstrate the cellular basis for the maintenance and termination of tolerance; describe the nature of the antibody produced in tolerant animals following termination of tolerance in terms of specificity and structure. This project was so designated to promote further understanding of the basis of immunological tolerance, the events occuring during termination, and the possible mechanisms of autoimmunity.